package com.wuyong.Chapter3;

public class LoopQueue<E> implements Queue<E> {

    private E[] data;
    private int front, tail;
    private int size;

    public LoopQueue(int capacity) {
        data = (E[]) new Object[capacity + 1];
        front = 0;
        tail = 0;
        size = 0;
    }

    public LoopQueue() {
        this(10);
    }
    @Override
    public void enqueue(E e) {
        if ((tail + 1) % data.length == front) {
            resize(2 * getCapacity());
        }
        data[tail] = e;
        size ++;
        tail = (tail + 1) % (data.length);
    }

    @Override
    public E dequeue() {
        if (isEmpty()){
            throw  new IllegalArgumentException("Queue is empty");
        }
        E e = data[front];
        data[front] = null;
        front = (front + 1) % data.length;
        size --;
        if (size == getCapacity() / 4 && getCapacity() / 2 != 0) {
            resize(getCapacity() / 2);
        }
        return e;
    }

    @Override
    public E getFront() {
        return null;
    }

    public int getCapacity() {
        return data.length - 1;
    }
    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return front == tail;
    }

    private void resize(int newCapacity) {
        E[] newData = (E[]) new Object[newCapacity + 1];
        for (int i = 0; i < size; i++) {
            newData[i] = data[(i + front) % data.length];
        }
        front = 0;
        tail = size;
        data = newData;

    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(String.format("LoopQueue: size = %d , capacity = %d\n", size, getCapacity()));

        sb.append("head [");
        for (int i = front; i != tail; i = (i + 1) % data.length) {
            sb.append(data[i]);
            if ((i + 1) % data.length != tail) {
                sb.append(", ");
            }
        }
        sb.append("] tail");
        return sb.toString();
    }

    public static void main(String[] args) {
        LoopQueue<Integer> arrayQueue = new LoopQueue<>();
        for (int i = 0; i < 20; i++) {
            arrayQueue.enqueue(i);
            System.out.println(arrayQueue);
            if (i % 3 == 2) {
                arrayQueue.dequeue();
                System.out.println(arrayQueue);
            }
        }

    }

}
